808.    ELEY, D. D., AND RIDEAL, E. K.  Catalysis of the Parahydrogen Conversion by Tungsten.  Proc. Roy. Soc. (London), vol. 178, A, 1941, pp. 429-451; Chem. Abs., vol. 36, 1942, p. 22.

     The p-H₂ conversion was measured on the surface of W as a function of the surface concentration of adsorbed O acting as a poison.  The O decreases the fraction of the metal surface available for reaction and affects the reactivity of the neighboring chemisorbed hydrogen. Dipole-dipole interaction between the adsorbed atoms may be an important factor in this.  A part of the O adsorbed on W can be removed at room temperature by reaction with H₂.  Films of CO, N₂, and C₂H₄ also act as poisons, and it appears that the small conversion that takes place when they are present is due to the formation of a hydride surface on top of the film rather than on gaps in it.  Constants for the reaction are calculated, including the temperature-independent factor for the zero order reaction.  The reaction is considered in terms of the activated complex theory and is shown to be more in accordance with a conversion mechanism based upon an interchange between loosely adsorbed H₂ molecules and chemisorbed H than with the original idea of the recombination of chemisorbed H₂ atoms.  The H₂+D₂ reaction has the same rate as the p-H₂ conversion; hence tunneling in the potential barriers plays an unimportant part in this H₂ reaction, even at –150°.  The H₂+D₂ reaction has about the same activation energy as the parahydrogen conversion.  This, measured at 1.3 mm., is 3,070 cal.  The 2 reactions are kinetically identical and go through the same mechanism.

     ELFSTROM, N.  See abs. 1623.